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Undeleted > Spectroscopy > Flashcards

Spectroscopy Flashcards

1
Q

What are the 5 components of optical spectroscopy

A
  1. Stable source of Radiant energy
  2. Transparent container for sample
  3. A device that isolates specific region of spectrum
  4. Radiation detector
  5. Signals processor and readout
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2
Q

Draw the gerneral layout for an optical spectroscopic method based on ABSORPTION

A
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3
Q

Draw the gerneral layout for an optical spectroscopic method based on FLUORESCENCE

A
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4
Q

Draw the gerneral layout for an optical spectroscopic method based on EMISSION

A
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5
Q

What are optical spectroscopic methods based on (total of 6)

A
  1. Absorption
  2. Fluorencence
  3. Phosphorensence
  4. Scattering
  5. Emission
  6. Chemilumenescence
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6
Q

What is Spontaneous Emission?

A

When an atom spontaneously jumps into a state with lower energy via the emission of a photon

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7
Q

What is Stimulated Emission?

A

When an atomic electron goes to a lower state after interracting with an elecromagnetic wave of a certain frequency via the emission pf a photon with the same phase, frequency, wavelength. etc..

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8
Q

What is a photon?

A

a stream of discrete “particles” or “wave packets of energy”

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9
Q

The energy of a photon is proprotional to the _________ of the radiation.

A

frequency

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10
Q

What is the wave nature of a single frequency electromagnetic beam?

A

The electric field oscillates in a **plane perpendicular **to the magnetic field, in a plane-polarized wave.

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11
Q

What happens to the electric field if radiation is unpolorized?

A

a component of the electric field would be seen in **all planes. **

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12
Q

what is Planck’s constant (**h) **?

A

6.63 x 10-34 J•s

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13
Q

1 J = _____ ev (electron volts)

A

______ J = 6.24 x 1018ev

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14
Q

What is the equation for frequency?

A

frequency= speed of light/ wavelength

v = c/λ

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15
Q

What is the equation for **Energy? **

A

Energy = Planck’s constant • fequency

E=hv

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16
Q

What is the equation to find refractive index?

A

Refractive index = (velocity in vaccum) **/ **(velocity in medium)

ni= c/vi

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17
Q

What is dispersion?

A

The variation in refractive index of a substance with wavelength or frequency

(ie. when a wavelength changes, so does the refractive index.)

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18
Q

What are the two types of regions in dispersion plots?

A

normal and anomalous dispersion region

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19
Q

how does a normal dispersion region look on a dispersion plot?

A

there is a gradual increase in refactive index w/ increasing frequency (or decreasing wavelength)

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20
Q

how does a anomalous dispersion region look on a dispersion plot?

A

there are sharp changes in the refractive index on the dispersion plot

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21
Q

what is **black body radiation? **

A

The continous emission spectrum of a substance when heated to incandescence.

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22
Q

Define **Relaxation. **

A

when an atom or molecule goes from excited state energy level to a lower energy level

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23
Q

What is Stoke’s Shift?

A

the negative difference in frequencies of emitted radiation from the incident beam.

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24
Q

The lowest state of a molecule is reffered to as _________.

A

ground state

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25
Q

What is spectroscopy?

A

the study of the interraction of various types of radiation with matter.

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26
Q

concerning waves, what is a period?

A

The time in seconds required for a particle a medium to make one complete vibrational cycle.

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27
Q

concerning waves, what is frequency?

A

The number of **vibrational cycles **per second

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28
Q

what is wavelength?

A

the distance between to maximas

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29
Q

what is the velocity of a wave dependent on?

A

The medium it’s passing through

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30
Q

Frequency is the inverse of _______

A

Period is the inverse of ______

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31
Q

what is a vaccum?

A

the absence of a medium

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32
Q

True or False?

excess energy can be released by heat.

A

TRUE

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33
Q

What is the name of this diagram?

A

Jablanski Diagram

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34
Q

what is the result of a jablanski diagram?

A

A SPECTRUM

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35
Q

what is the quantum theory?

A

atoms/moleules/ ions have limited number of discrete energy levels

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36
Q

Total Energy is the sum of __________

A

Eelectronic + Evibrational + Erotational

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37
Q

What is non-raidative relaxation?

A

loss of energy in small steps

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38
Q

Which relaxes faster, Fluorescence or Phosphorescence?

A

Fluorescence.

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39
Q

How does Stokes shift occur?

A

When a certain energy is put in a sample, you should get less energy out therefore the wavelength should be longer

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40
Q

How does Anti-Stokes shift occur?

A

When you put in a certain amount of energy in a sample, and end up getting MORE energy out. therefore having a shorter wavelength.

This can occur when heat is added

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41
Q

What are the four major categories of spectrochemical methods.

A
  1. Emission
  2. Luminescence
  3. Scattering
  4. Absorption

*all require radiant power, P *

42
Q

Equation of Transmittance?

A

**T = (P/P0) x 100% **

43
Q

What is the equation for Absorbance?

A

A = -log10T

A = log(P0/P)

A = 2 - log10%T

A= εbc

44
Q

What is Beer’s Law?

A

Absorbance = [molar absorbitivity L •mol-1 •cm-1] [path length cm] [concentration of analyte]

A= εbc

45
Q

Beer’s law is _________ for mixtures at a given wavelength

A

**Additive **

46
Q

What are the limitations to Beer’s Law

A
  • Only for dilute solutions
  • Monochromatic radiation
  • Path length must be the same

**high concentrated analyte makes it hard for absorption of radiation to happen**

47
Q

Draw the general layout for a single beam instrument

A
48
Q

Draw the general layout for a double beam-in-space instrument

A
49
Q

Draw the genral layout for a double-beam-in-time instrument

A
50
Q

what is a charged coupled device (CCD)

A

is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated.

integrated circuit etched onto a silicon surface forming light sensitive elements called pixels. Photons incident on this surface generate charge that can be read by electronics and turned into a digital copy of the light patterns falling on the device. like cellphone cameras

51
Q

What is a Charge injection Device (CID)

A

A charge-transfer device used as an image sensor in which the image points are accessed by reference to their horizontal andvertical coordinates

52
Q

Draw a general diagram of a photodiode array

A
53
Q

What are the two types of wavelength selectors

A
  1. Filters
  2. Monochromators
54
Q

What type of filters are there? Order from least best to best.

A
  1. Absorption Filters (inefficent)
  2. Interference filters (very effeicent)
  3. Holograohic Notch Filter (best)
55
Q

what does a monochromator consist of.

A
  1. Entrance Slit
  2. Collimating lens OR Mirror
  3. Prism OR Grating to dispense radiation
  4. Focusing element
  5. Exit Slit
56
Q

what does a **Photomultiplier Tube (PMT) **do?

A

Amplifies signals which allows for sensitive detection.

57
Q

Photomultiplier tube is based on the ___________ ______ by _________ .

A

Photoelectric effect; Einstein

58
Q

Define electron cascade.

A

propagation of electrons, build up of electrons.

59
Q

What would be most likely used as optical source for wavelength of 200-400 nm

and what type of Electromagnetic radiation is in that region?

A
  • H2 or D2Lamp (moest likely deterium lamp)
  • UV
60
Q

What would be most likely used as optical source for wavelength of 400-700 nm

and what type of Electromagnetic radiation is in that region?

A
  • a Tungsten Lamp
  • Visible light
61
Q

what does laser stand for?

A

Light Amplification by stimulated emission of radiation

62
Q

What are the four important prcoesses in laser action

A
  1. Pumping
  2. Spontaneous emission
  3. Stimulated Emission
  4. Absorption
63
Q

what is pumping

A

excitation by electrircal, radiant, or chemical energy

64
Q

What must happen in order for light amplification to occur?

A

the number of photons produced by stimulated emisssion must **exceed **the number lost by absorption. known as popultion inversion

(Ie. THERE IS MORE ENERGY IN THE EXCITED STATE THAN IN THE LOWER ENERGY STATES)

65
Q

Population inversions are created by _______.

A

Pumping

66
Q

Define what happens to produce a Three-Level Laser system

A

The transition for a laser radiation is between an excited state and the ground state

67
Q

Define what happens to produce a Four-Level Laser system

A

there is an additonal excited state between the most excited state and ground state

68
Q

What is the advantage of a four level laser system?

A

population inversions are achieved more easily, which is essential laser action

69
Q

Repilca gratings are manufactured from a _______ _ ._

A

master grating

70
Q

what is the equation for constructive interference?

A

diffrection order•wavelength =distance betweenn reflective sufaces( sin Ө1+ sin Ө2)

nλ = d(sin i + sin r)

71
Q

What is the effective bandwidth of a filter

A

one half the bandwidth when the two slit widths are identical

72
Q

what does a PMT consist of?

A
  • photocathode
  • Dynodes
  • Anode
  • Amplified Current

**in a vaccum tube**

73
Q

Draw the basic structure of a PMT

A
74
Q

What does a photocathode do?

A

Converts light (photons) into an electron current

75
Q

What does a dynode do?

A

dynodes serve as an electron multiplier

76
Q

what does an anode do?

A

delivers an output signal

77
Q

1 Å = _____cm

A

_____Å = 10-8cm

78
Q

1 m = _____nm

A

____m = 109 nm

79
Q

10 Å = ____ nm

A

_____Å = 1 nm

80
Q

1 MHz = ______Hz

A

______MHz = 106Hz

81
Q

1 mol = ______photons

A

____ mol = 6.02 x1023 photons

82
Q

1 m = ______ µm

A

_____ m = 106 µm

83
Q

what is coherent radiation?

A

the phases of two waves that represent radiation differ by a known constant.

84
Q

what is the work function of a substance?

A

the energy required to remove an electron from the surface of a substance

85
Q

Define Photoelectric effect.

A

The energy contained inn a wave and particles depends on the frequency and intensity

86
Q

what is the equation used to find refractive index when given angles

A

refractive index = (angle of incidence of “x”) / (angle of refraction of “x”)

nx= sin Өix**/ **sin Өrx

87
Q

Equation to calculate concentrations in two unknown solutions

A

A1= (εm1•b•cm) + (εn1•b•cn)

A2= (εm2•b•cm) + (εn2•b•cn)

88
Q

Equation to calculate the new concentration of a sample

A

Cx = (A1•Cs•Vs) **÷ **(A2- A1)Vx

89
Q

why are holographic notch filters the best?

A

they provide a much narrower bandwidth and higher intensities

90
Q

absorption flters are mainly used for what region?

A

visible regions

91
Q

what is a disadvantage of using abosption filters?

A

they often block a significant portion of desired radiation

92
Q

what is the range on a spectrum where visible light seen? (in nm)

A

400-700nm

93
Q

Which source of energy is good for wavelengths from 160-380 nm

A

H2and D2Lamp

94
Q

Which source of energy is good for wavelengths from 320-2400 nm?

A

tungsten lamp

95
Q

Which source of energy is good for wavelengths from 200-1000nm

A

Xe arc Lamp

96
Q

Which source of energy is good for wavelengths from 0.4-20 µm ?

A

nernst glower

97
Q

Which source of energy is good for a line source of UV/Visible?

A

hollow cathode lamp

98
Q

Which source of energy is good for a line source of UV/Visible/IR?

A

Lasers

99
Q

__________ grating consists of ~300 blazes/min

A

Echelle

100
Q

__________grating consists of ~1300 blazes/min

A

echellete

101
Q

What are the units for reciprocal linear dispersion?

A

nm/mm

OR

Å/mm

Undeleted (34 decks)

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